VSO is a three-letter acronym with multiple meanings, as described below:
- Voluntary Service Overseas, an international development charity
- Valdosta Southern Railroad
- Vancouver Symphony Orchestra, a Canadian orchestra performing in Vancouver, British Columbia
- Variable Speed Oscillator
- Verb–subject–object in Linguistic typology
- Vermont Symphony Orchestra, a symphony orchestra based in, and supported in part by, the U.S. state of Vermont. It is a 501(c)(3) corporation. It is one of the few, and the oldest, state-supported symphony orchestras in the United States
- Victoria State Opera, Australian opera company, merged in 1996 with Opera Australia
- Vienna State Opera, an opera house – and opera company – with a history dating back to the mid-19th century
- Vienna Symphony Orchestra
- Volvo Super Olympian (Volvo B10TL), double-decker bus
- Video du Sud Ouest, a French software company known as VSO Software, specialized in video conversion, burning and photo applications, selling worldwide
- Very Superior Old (VSO designation on brandy or port bottles indicating an age of 12–17 years)
- The Virtual Solar Observatory, a federated search system for solar physics images.
- Violin-Shaped Object, a pejorative term for a low-quality instrument.
In aviation, VSO is an aircraft's stall speed in the landing configuration